Not a fan of this pairing because it doesn't do anything new or better than what we already had. Half of reason the older friend was interesting was because she was aloof and liked to tease Igarashi. Now the teasing's been claimed by the other office couple and this one feels like a copy of the same dynamic. And while Kazama and Sakurai have shifting moments of confidence, embarrassment and vulnerability, Natsumi seems to always win her engagements, whether it's with other adults or the kid. It leads to a boring coupling. It seems like the only memorable matching trait between them is that they're both really attractive people. And their eye and hair colors match.
It'd be something else if Yuu was normally the bold and confident leader of his group of friends but always tripped around the older girl or if Natsumi was constantly making mistakes around the boy but bluffing her way into making everyone think they were intentional choices. But as it is, it's a puppy dog chasing after a Mary Sue, with no signs of progressing the characters any time soon.